Tag Archive | "RMS"

Review – Agilent U1272A True-RMS Digital Multimeter

This is our review of the Agilent Technologies U1272A water and dust resistant digital multimeter. It’s an extremely well specifed instrument, and according to the Agilent promotional material a better alternative to the venerable Fluke 87V. We also have examined the Bluetooth module.

Initial impression

The retail box as always is impressive and well decorated. Opening it up reveals a range of items:

contentsss

including the meter itself, a calibration certificate and calibration results sheet, probe set, thermocouple, quick start guide and four AAA cells. It was a little disappointing to not find alligator clip adaptors nor a carrying case. For those interested, a full range  of documentation is available here.

The meter measures 207 x 92 x 59 mm (hwd) and is quite solid, not too heavy and surrounded by a good orange non-slip rubber layer. This no doubt helps provide some shock resistance, as this unit has survived a 2.5 meter drop from my ceiling to the concrete. It is refreshing to see that the keypad is laid out in an organised way, much better than the random-looking layout on the U1250 series:

meterss

The meter

Installing or changing the the battery (four AAA cells) is easily accomplished, and thankfully the fuses are also in the same compartment. The included AAA cells are thecheaper “GP brand”, and should do for the first few months. The dust and moisture protection is evident as shown by the o-ring seal around the perimeter of the compartment:

batteryfusecompartmentss

As mentioned earlier, the U1272A is water and dust resistant to IP54 specifications – 54 meaning “protected against dust limited ingress”/”protection against water sprayed from all directions – limited ingress permitted.”.

For more information about IP ratings and what they all mean, check out this IP-rating chart.

It is possible to turn the function selector with one hand whether you have the meter standing up or laying on your desk. The included test leads are just over 1200mm in length and are rated at Cat III 1000V, 15A. Two pairs of probes are included, with 4mm and 19mm tips:

leadsprobesss

Again, it is unfortunate that alligator-clip adaptors nor probes are included – these are very useful especially to those who are colourblind and need to sort resistors or measure tiny through-hole capacitors. Furthermore, a K-tyle thermocouple and non-compensation transfer adaptor are also included:

thermocoupless

The thermocouple’s temperature range is -20~200 degrees Celsius, however with an optional thermocouple the maximum temperature can be increased to 1200 degrees C. As for the othermeasurement ranges, they are detailed in the data sheet which you can download here (.pdf).

Furthermore there is a diode test  function, and a continuity beeper. The backlight also flashes when using the continuity function which would be very convenient for those working in a noise environment. There has been some discussion around various forums as to the speed of the continuity function, so here is a small video demonstration of it in action:

In use

Although readers would not have any problem using the meter without reading the manual, doing so will illustrate the particular features of the U1272A as well as operation of the menu system that allow various settings to be changed. These can include: beep frequency (!), backlight duration, data communication parameters, default temperature units, scale conversion values, and activating the low-pass filter available when measuring DC voltage and current.

At the risk of shortening the battery life, I extended the backlight duration immediately to thirty seconds; and set temperature units to degrees Celsius. When taking measurements that only require the main numeric display, the ambient temperature is shown in the secondary numeric display. I must admit to discovering another feature by accident, if the leads are in the current and COM terminals and you select a non-current measurement function – the meter will beep like crazy, blink the backlight and show an error message. This is useful when you’re tired and probably should be doing something else.

Measuring AC voltage provides various data upon request. Apart from the RMS voltage value, you can also turn on a low-pass filter which blocks unwanted voltage above 1 kHz.

The frequency measurement function allows the display the frequency, duty cycle and pulse-width when measuring AC or DC current or voltage. Furthermore, you can display both voltage/current and also display the frequency, pulse-width and duty cycle at the same time, for example:

freqvoltss

In a previous article the U1272A was used to measure frequency and duty cycle, which you can observe in the following short clip:

Measuring DC voltage is straightforward, and there is also the option to measure both AC and DC components and display them combined or separately, for example:

acvoltdcoffsetss

You can also display voltage as a decibel value relative to 1 mW (dBm) or a reference value of 1V (dBv). And the dB reference impedance can also be set to fall between 1 and 9999 ohms. Another interesting voltage measurement function is “Zlow”. Using this function, the meter changes to a very low input impedance, and can remove “ghost” voltages from the measurement by dissipating the coupling voltage. This function can also be used to test if a battery is still usable, if the voltage of the battery under test decreases slowly, it doesn’t have the capacity to deliver the required voltage. However I wouldn’t put a battery under this test method for too long due to the meter acting close to a short circuit.

Measuring resistance is simply done with the U1272A, and for more precise measurements one can short the probes to measure their resistance then set a null point so your measurements will not be affected by probe resistance. There is also an Agilent feature called SmartOhm which can be used to remove unexpected DC voltages that can add errors to resistance measurements. You can also use SmartOhm to measure leakage current or reverse current for junction diodes. I look forward to spending more time examining SmartOhm.

Furthermore, one can also measure conductance (the reciprocal of resistance) which is measured in Siemens. According to the manual one can measure extremely high resistance values up to 100 gigaohms. Interesting.

Diode measurement works as expected, the standard setting displays the voltage drop across the diode. However by pressing Shift on the meter, you can use the “Auto-diode” function which forward and reverse bias simultaneously using both numeric displays. For example, measuring a 1N4004 diode produces the following display, the forward voltage and the Good/Not good result:

autodiodess

Measuring capacitance is also quite simple, and the manual recommends setting a null value while the probes are open to compensate for residual capacitance. Interestingly the LCD shows when it is charging and discharging the capacitor under test, using the following segments:

capsegss

Temperature measurement is possible with the included thermocouple and adaptor. Note that the included K-type thermocouple is only rated for up to 200 degrees Celsius, however with an optional unit the meter can measure up to 1372 degrees C. The display can show Fahrenheit as well as Celsius. The meter also shows ambient temperature using the secondary numeric display when it is not in use with other measurement display functions. Finally, measuring AC or DC current is completed as expected, and as noted earlier when switching to another non-current function, the meter will remind you to change the positive lead.

Compared to other meters, there are a few things that irritated me slightly with this unit. The auto-ranging can be somewhat slower than other meters, especially the frequency measurement – it can take around four seconds to measure a constant frequency… my old Tektronix CFC-250 is faster than that. And the exclusion of alligator-clip adaptors and case was disappointing considering the price of the meter. However on a positive note, the meter is supplied with minimal paper documentation, and a full range of manuals, service guides and so on are available for download from the Agilent website.

Update – 14th June 2011

Turns out that many people had similar (and other problems) to myself with their U1272A. They can be solved by updating the firmware via the USB cable. Agilent will send owners of early versions with the affected firmware a free USB cable in order to fix it up. Download this .pdf file with the instructions on how to receive the cable.

Update – 20th June 2011

The USB>DMM cable has arrived and the firmware updated to v2.0. The meter now works as expected – very well. Kudos for Agilent for taking ownership of the problem and sorting it out so rapidly.

Over the last three months I have been using the U1272A and would call it a success. The dual line LCD display really is useful, as well as the low current measurement and especially the Zlow function. There is a short video you can watch that explains a few of the unique features very well. Furthermore, there is a distinct lack of fragility which gives you one less thing to worry about when looking after your tools. Finally there is also the data-logging, however this does require an optional cable. If you are in the market for a full-function electronics multimeter, put this meter on your evaluation list.

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts, follow on twitter, facebook, or join our Google Group.

High resolution images are available from flickr.

[Disclaimer – the Agilent U1272A in this review is a sample made available by Agilent Technologies via element-14]

Posted in agilent, android, bluetooth, multimeter, review, test equipment, tutorial, U1177A, U1272AComments (2)

Review – Fluke 233 Remote Display True RMS Multimeter

Hello readers

Several followers of my website have noticed the use of an interesting multimeter in a few of my articles, and were curious about it. So in this article we will discuss it in more detail. It is certainly novel in design, and has proven to be very convenient in use – the Fluke 233 remote-display true RMS multimeter. It arrives in a cardboard box that is easily recycled:

boxs

Upon tearing open the packaging we are presented with the following contents:

contentss

The contents of the box are as follows:

  • The meter itself;
  • a long (~1.2m) pair of Cat IV leads with very sharp points;
  • matching insulated alligator clip adaptors;
  • a K-type thermocouple;
  • a printed Getting Started manual, and the complete manual on CDROM;
  • a single, universal getting started sheet – explains how to remove battery isolation tabs.

However, a carry case was not included. Considering the cost of the meter here (Au$550 + tax), one would have expected a case. On the other hand, if you/your workplace can afford a 233, you can pay for your own case. So there’s two angles to the case perspective.

It is good to see that there isn’t too much of a printer manual, the less paper used the better. As others have said, if you have one of these meters the manual isn’t necessary apart from checking the specifications, and the same applied to myself. Thoughtfully the meter is supplied and fitted with 5 x AA Duracell alkaline cells, three in the meter body and two in the display unit. All one needs to do is pull out the plastic tabs from the battery compartments, and you’re ready to go.

Physically the unit does not disappoint. Made in the USA. First class. Another solid Fluke design, clean lines, and a great fit and finish. Futhermore it is of a good weight, so you could always bang in a nail with it, or the pointy-head boss. The exterior has the rubber-moulded housing which is not removable, however this would be recommended for the target market – as the 233 would be more of a field work than a test-bench instrument. However, if you do sit it on the bench with the tilting bail, you can still operate it with one hand as it has enough friction to stay put. It is also good to see that the box and packaging are cardboard which is easily recycled.

After flicking the meter on the first thing to do was remove the display, plug in the thermocouple, and toss the body into the freezer:

freezer-tests

Even with the meter in the freezer, I could still move the display around 1.5 meters away and it still received the data signal. Notice how the display is on the freezer door – it is magnetic. Immediately the benefits of the remote display come to mind. You can always have the display right where you want it, and the meter where it needs to be… it’s win-win. After showing it to my auto-electrician friend, she didn’t want to give it back.

The ability to set up a meter in a less than perfectly safe environment and take the display away is almost priceless. Furthermore, the backlight is a nice even blueish colour, and times out after around forty seconds. Whilst in the kitchen, I tested out the external temperature of my tea:

teas

Using the meter in general is very simple, you can hold it in one hand and select all of the functions with your thumb. Having the yellow shift key makes changing between associated readings very simple, for example after reading AC voltage:

241vacs

Then pressing the shift key changes to frequency:

50-hzss

The meter has several useful indication functions – while working with high voltages the triangular market is illuminated; when changing to temperature you are prompted with “OPEN” for the thermocouple, and changing to current you are prompted with “LEAD” to change sockets. It is obvious after a short period of time this was designed by engineers for engineers, and not made to a ‘price’. Although this is not an electronics multimeter, it still has quite a few ranges that would suit at a pinch. Plus the one-touch data hold, minimum and maximum functions are included as with other top-end Flukes. Hopefully someone at Fluke is working on a remote display version of their 87V.

Now that I have had this meter for just over five months, it has already become a worthwhile addition to my bench. For the kind of work I do, it has already replaced another multimeter, my old frequency counter and thermometer. The ranges are quite useful, and the continuity beeper is in the display not the body. According to the manual the 233 is rated for a one meter drop onto any of the six surfaces. Out of respect to the meter I will not throw it into a river or from a moving car. The other factor that prevents me from going to such extremes is the clear plastic over the LCD – there is a small amount of ‘give’ or flexibility in that area. Otherwise the 233 is as solid as they come.

The specifications can be found in detail in the manual here, however a quick glance shows:

Range                                                             Accuracy

AC voltage: 0.1mV ~ 1000V                      1~2%+3

AC current: 1mA ~ 10A                               1.5%+3

DC voltage: 0.1mV ~ 1000V                     0.25%+2

DC current: 1mA ~ 10A                               1.0%+3 ** no microamperes

resistance: 0.1 ~ 40 meg-ohm                   0.9~1.5%+2

frequency:  0.01 Hz ~ 50 kHz                    0.1%+2

capacitance: 1nF to 9999 uF                     1.9%+2

temperature: -40 ~ 400 degrees Celsius     1%+10

And there is also a diode test and continuity beeper function. Interestingly enough, I discovered by accident that the frequency counter function was slightly underrated. Some more testing showed it was good for up to 99.48 kHz:

233_freq

Not bad at all. However as with the many pros, there are  a few cons to using this meter. The auto-zero time of the display is a little slow, sometimes it can take two seconds. That doesn’t sound like much, but when you’re measuring many components the time adds up. And the LCD is not protected as well as expected, you can push into it with your finger. For a Fluke meter, one would expect it to be much more solid – if the display unit fell from a height and landed on something pointy with the display facing down, it would be ruined. So be careful if you have one.

Furthermore, the battery life is around eight to ten weeks of “daily use” (perhaps seven hours a week, usually with the backlight on). Some have said this is bad, however my opinion is that the convenience of the remote display makes up for the shorter battery life.

However at the end of the day – this is a great tool. Being able to measure something outside your field of vision, and having the results in front of you is incredibly useful. You could achieve the same functions by using a meter with a PC interface, but that can be overkill and time-consuming to set up. So if the specifications of the 233 meet your needs, this is a great tool that will serve you very well.

The Fluke 233 Remote Display True RMS Multimeter is available from your local element-14 or Fluke distributor.

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts. Or join our Google Group.

[Disclaimer – the Fluke 233 is a review sample made available by Fluke via element-14]

Posted in 233, fluke, learning electronics, product review, test equipmentComments (6)

Education – Introduction to Alternating Current

Hello everyone!

Today we are going to introduce the basics of AC – alternating current. This is necessary in order to understand future articles, and also to explain in layperson’s terms what AC is all about. So let’s go!

AC – Alternating Current. We see those two letters all around us. But what is alternating current? How does current alternate? We know that DC (direct current) is the result of a chemical reaction of some sort – for example in a battery, or from a solar cell. We know that it can travel in either direction, and we have made use of it in our experimenting. DC voltage does not alter (unless we want it to).

Therein lies the basic difference – and why alternating current is what is is – it alternates! 🙂 This is due to the way AC current is created, usually by a generator of some sort. In simple terms a generator can be thought of as containing a rotating coil of wire between two magnets. When a coil passes a magnet, a current is induced by the magnetic field. So when the coil rotates, a current is induced, and the resulting voltage is relative to the coil’s positioning with the magnets.

For example, consider the diagram below (exploded view, it is normally more compact):

generator

This is a very basic generator. A rotating coil of wire is between two magnets. The spacing of the magnets in real life is much closer. So as the coil rotates, the magnetic fields induce a current through the coil, which is our alternating current. But as the coil rotates around and around, the level of voltage is relative to the distance between the coil and the magnet. The voltage increases from zero, then decreases, then increases… as the coil constantly rotates. If you were to graph the voltage level (y-axis) against time (x-axis), it would look something like below:

sin1

That graph is a sine wave… and is a representation of perfect AC current. If you were to graph DC voltage against time, it would be a straight horizontal line. For example, compare the two images below, 2 volts DC and AC, shown on an oscilloscope:

2v-dc-cro-small

2 volts DC

The following clip is 2 volts AC, as shown on the oscilloscope:

So as you can see, AC is not a negative and positive current like DC, it swings between negative and positive very quickly. So how do you take the voltage measurement? Consider the following:

sin2

The zero-axis is the point of reference with regards to voltage. That is, it is the point of zero volts. In the oscilloscope video above, the maximum and minimum was 2 volts. Therefore we would say it was 2 volts peak, or 2Vp. It could also be referred to as 4 volts peak to peak, or 4Vpp – as there is a four volt spread between the maximum and minimum values of the sine wave.

There is another measurement in the diagram above – Vrms, or volts root mean squared. The Vrms value is the amount of AC that can do the same amount of work as the equivalent DC voltage. Vrms = 0.707 x Vp; and Vp = 1.41 * Vrms. Voltages of power outlets are rated at Vrms instead of peak as this is relative to calculations. For example, in Australia we have 240 volts:

241vacs

Well, close enough. In fact, our electricity distributor says we can have a tolerance of +/- 10%… some rural households can have around 260 volts. Moving on…

The final parameter of AC is the frequency, or how many times per second the voltage changes from zero to each peak then back to zero. That is the time for one complete cycle. The number of times this happens per second is the frequency, and is measured in Hertz (Hz). The most common frequency you will hear about is your domestic supply frequency. Australia is 50 Hz:

50-hzss

… the US is 60 Hz, etc. In areas that have a frequency of 60 Hz, accurate mains-powered time pieces can be used, as the seconds hand or counter can be driven from the frequency of the AC current.

The higher the frequency, the shorter the period of time taken by one cycle. The frequency and time are inversely proportional, so frequency = 1/time; and time – 1/frequency. For example, if your domestic supply is 50 Hz, the time for each cycle is 1/50 = 0.02 seconds. This change can be demonstrated quite well on an oscilloscope, for example:

In the video above there is 2 volts AC, and the frequency starts from 100 Hz, then moves around the range of 10 to 200 Hz. As you can see, the amplitude of the sine wave does not change (the height, which indicates the voltage) but the time period does alter, indicating the frequency is changing. And here is the opposite:

This video is a demonstration of changing the voltage, whilst maintaining a fixed frequency. Thus ends the introduction to alternating current. In the next instalment about AC we will look at how AC works in electronic circuits, and how it is handled by various components.

I hope you understood and can apply what we have discussed today. As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement.

Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts. Or join our Google Group and post your questions there.

Posted in AC, alternating current, education, learning electronics, lesson, safety, tutorialComments (0)


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